Last-minute mergers endanger drivers, worsen traffic jams

Commuters cut into a right turn lane on Oak Street just before Octavia Boulevard in San Francisco, Calif. on Wednesday, Aug. 27, 2014. Some motorists cut into the right turn lane at the last minute - or make an illegal right turn from the left lanes - creating large backups and irking other drivers. less

Commuters cut into a right turn lane on Oak Street just before Octavia Boulevard in San Francisco, Calif. on Wednesday, Aug. 27, 2014. Some motorists cut into the right turn lane at the last minute - or make an ... more

Photo: Paul Chinn, Staff / The Chronicle

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Commuters turn right from Oak Street onto Octavia Boulevard in San Francisco, a stretch where many motorists try to cut in line.

Commuters turn right from Oak Street onto Octavia Boulevard in San Francisco, a stretch where many motorists try to cut in line.

Photo: Paul Chinn, The Chronicle

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A message is sprayed on the sidewalk at the intersection of Oak Street and Octavia Boulevard in San Francisco, Calif. on Wednesday, Aug. 27, 2014. Some motorists turning on Oak onto Octavia cut into the right turn lane at the last minute - or make an illegal right turn from the left lanes - creating large backups and irking other drivers. less

A message is sprayed on the sidewalk at the intersection of Oak Street and Octavia Boulevard in San Francisco, Calif. on Wednesday, Aug. 27, 2014. Some motorists turning on Oak onto Octavia cut into the right ... more

Photo: Paul Chinn, The Chronicle

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A commuter makes an illegal right turn onto Octavia Boulevard at the last second from a left lane on Oak Street in San Francisco, Calif. on Wednesday, Aug. 27, 2014. Some motorists cut into the right turn lane at the last minute - or make an illegal right turn from the left lanes - creating large backups and irking other drivers. less

A commuter makes an illegal right turn onto Octavia Boulevard at the last second from a left lane on Oak Street in San Francisco, Calif. on Wednesday, Aug. 27, 2014. Some motorists cut into the right turn lane ... more

Photo: Paul Chinn, The Chronicle

Last-minute mergers endanger drivers, worsen traffic jams

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It's the jerk merge.

San Francisco's streets are rife with drivers who, impatient with the slow pace of the commute, speed ahead of motorists in the proper lanes and then, at the very last moment, yank their wheel and cut over.

The illegal move - which most often happens at freeway on-ramps - typically goes unpunished and, according to some experts, may exacerbate city's already horrendous traffic problems.

The dynamic punishes law-abiding citizens who sit and wait, while rewarding the scofflaws who save valuable time. It can tempt many an affable commuter to turn into a menacing motorist.

"They cut you off," said 41-year-old Jackie Pham, who lives in Daly City and works in downtown San Francisco. "I can't stand that. Sometimes I purposefully won't let them in, so they don't feel like they can get away with it every time."

During the morning drive time, dozens of motorists every hour pull the jerk merge on Oak Street, a four-lane, one-way street running east from Golden Gate Park to Market Street.

Drivers planning to turn right on southbound Octavia Boulevard and launch onto the Highway 101 on-ramp are supposed to be in the rightmost two lanes. But others use the left lanes - meant for drivers going straight ahead - to speed to the front of the backup and zip over at the last second.

Come quitting time, drivers heading onto the Bay Bridge from San Francisco pull the move at almost every downtown on-ramp.

Adding to commute

Wayland Mok, 30, lives in the East Bay and works downtown. Like Pham, he tries not to drive to work, but every now and then he braves the rush-hour battle royal, which he said can stick him in traffic for almost 45 minutes before he even gets on the bridge.

"Sometimes I find myself in that situation," Mok said. "Do I wait in line or cut someone off? It's 50-50."

Cutting in line may be saving those drivers time, but for everyone else trying to navigate the city's tangled streets, it means more minutes behind the wheel. The perilous merge is also dangerous for nearby drivers, cyclists and pedestrians who could get plowed into.

Michael Cassidy, a professor at UC Berkeley's Civil and Environmental Engineering department, has studied the phenomenon on Bay Area highways by carefully measuring freeway traffic with sensors and cameras.

'Most disruptive'

Cassidy said the same principles apply to city streets.

"Of all the maneuvers, it's probably the most disruptive to traffic," he said of the shenanigan. "If the police were to say, 'We're going to crack down on one type of maneuver,' that would be the one. It would likely have the most significant effect on traffic."

The move not only worsens traffic jams in the lanes the driver cuts off, but backs up the lanes the driver borrows as a slingshot, he said.

The move is different than the so-called zipper method, which was tested by traffic engineers in states like Minnesota. In that model, cars are directed to merge at a single point from multiple lanes to reduce the length of the backup.

There is no specific state law describing the jerk merge, but police can cite drivers for a number of moving violations, including making an unsafe lane change, failing to signal or running a red light.

Enforcing those laws, though, is not identified as a priority by San Francisco police.

"All of our officers on patrol will enforce violations," said Officer Albie Esparza, a department spokesman. "But our priorities are other things such as pedestrian right-of-way, school zones and speeding."

Esparza said many of the department's actions are complaint-based, and different neighborhoods have different needs. The police have a limited number of officers they can send to enforce traffic violations.

Paul Rose, a spokesman for the San Francisco Municipal Transportation Agency, said traffic engineers are aware of drivers who jump ahead and are always looking for ways to improve traffic.

"At times we can install barriers," he said, "but on an urban street, you have cross alleyways, intersections and driveways, so you can't barricade the queue.

What's more, Rose said engineers are aware of the problems at the right turn lanes on Oak Street at Octavia Boulevard and will soon add a third right turn lane.

Though she gets frustrated by last-moment mergers, Pham believes many have less nefarious motives. Some, she said, may be confused out-of-towners or people not familiar with San Francisco's urban grid.

"It's hard to drive in the city now," she said. "I feel like it's just too many people in a small area."

What's not working

Issue: Impatient drivers heading for jammed freeway on-ramps in San Francisco often cruise past motorists waiting in line in the proper lanes and then pull a last-moment, dangerous, illegal merge.

What's been done: San Francisco police do not do special operations to stop last-second merging, but enforce traffic violations if they see them, officials said.